Safety inner tube



Filed Nov. 27, 1948 INVENTOR. 76/0/1170 (J F/Vdflfd" BY 391mg] ATTORNEY Patented Aug. 14, 1951 SAFETY INNER TUBE Thomas, J. Rhodes, Clifton, N. J., assignor to United States Rubber Company, New York, -N. Y., a corporation of New Jersey Application November 27, 1948, Serial No. 62,295

Claims.

This invention relates to a slow-deflation inner tube for pneumatic tires and more particularly to an inner tube having a series of chambers built into the tube which prevent rapid collapse of the tube when punctured.

It is an object of the invention to provide a new and improved inner tube provided with a series of interconnecting chambers extending along the interior of the tube and which hold the volume of air in the tube in a series of separate compartments so that when punctured the air escapes slowly through the separate compartments.

It is another object of the invention to provide an improved inner tube of the type described in which the air-retaining chambers are formed by three equally spaced partitions which are twisted along the length of the tube around the axis thereof in a helicoidal form.

A further object of the invention is the provision of an inner tube having several compartments or chambers which may be extruded in a single operation by conventional factory processes and in which splicing of the walls of the compartments and tube may be easily and quickly achieved thereby providing'a tube which maybe manufactured at low cost.

. In the accompanying drawing:

Fig. 1 illustrates a slow-deflation inner tube constructed in accordance with the invention with part of the tube being broken away in cross-section;

Fig. 2 is a sectional view through the inner tube taken along the line 22 of Fig. 1;

Fig. 3 is a sectional view of the tube illustrating how the tube may be folded for splicing;

Fig. 4 is a view in elevation of .a splicing jig used in manufacture of the inner tube, showing the tube clamped therein; and

Fig. 5 is a side elevation of two splicing jigs ready to be brought together to effect splicing of the tube.

Referring to the drawing, Figs. 1 and 2 illustrate an inner tube constructed in accordance with my invention and which comprises a conventional circular tube wall In the interior of which is divided into a plurality of chambers or compartments ll, 12 and I3. Referring to Fig. 7

2, the aforementioned chambers are formed by three, spaced, radially disposed partitions or webs M which radiate outwardly from the geometrical center [5 of the inner tube to equally spaced points IS on the circumference of the tube; The inner tube thus constructed may be extruded using aconventional die with the exception that the die is rotated so that as the outer tube wall I0 is formed the inner partition walls I4 will be twisted along the length of the tube to form, in effect, helicoidal forms of chambers. The arrangement of the chambers H, l2 and 13 along the length of the inner tube is shown by Fig. 1. A suitable form of extruding apparatus for manufacturing the inner tube is described in the copending application of Thomas J. Rhodes filed January 22, 1947, for Extruding Apparatus, Serial No. 719,867 now Patent No. 2,465,482 issued March 3, 1949. In manufacture, the tube wall with the associated inner partitions is extruded continuously; lengths of the tube are cut off and the ends spliced together to form the annular inner tube.

One outstanding advantage of the inner tube construction of the present invention is that the partitions I 4 are so formed and located as to facilitate the splicing operation so that airtight, smooth splices are provided without any distortion of the tube wall or partitions. To this end, the outer edges of the partitions l4 are formed integrally with the tube In at points l6 spaced equidistant around the circumference of the tube, such points being apart or, expressed mathematically, the length of the are between points I6 is of the circumference of the tube, or

where D again representsythe diameter of the tube section. Since each partition is thus cons'tructed with'a radial length equal to one-half of the arc subtended by two partitions, it is evident that the sum of the radial lengths of any two-partitions is equal to the minor arc sub the partitions under stress or strain. The flexi-- bility of the inner tube is also increased.

As a consequence of this construction, the 'extruded tube can be folded together for splicing by folding the outer tube wall inwardly against the partitions I I, as indicated by the arrows in Fig. 3, without any stretching or wrinkling of either the tube wall or the partitions. As a result, good strong splices can be obtained on the tube by rapid commercial splicing operations with a minimum of rejects due to improper splicing. In order to illustrate how the tube is spliced, the folded tube is shown in place in a jig ready for splicing inFigs. 4 and 5. An extruded length of the tube ID has been cut to suitable length and clamped in the jig between two movable jaws 20 and a stationary jaw 2|, each jaw having its working face suitably cut out in the form of a 120 angle to receive the tube as shown. When so clamped, the webs or partitions l4 lie perfectly fiat, and because of the relation between the length of the webs and the tube diameter, neither the webs I4 nor the tuberwall ID- are stretched or wrinkled, so that a clean splice, without any distortion or straining, is assured. The movable jaws 20 are disposed to slide in brackets 22 by movement of screws 23, which are threaded through holders 24. The fixed jaw 2| and the brackets 22 are suitably fastened to a frame 25, which has a port 26 for receiving the tube. The base 21 of the frame 25 is provided with slots 28 adapted to engage a rail 29 shown in Fig. 5, on which .two corresponding jig holders may be brought together in opposition to effect splicing of the tube ends in the conventional manner under heat and pressure to give the tube its annular configuration.

The three-chambered inner tube may be infiated by various means. The air may be introduced by means of a conventional valve stem 30 leading into one chamber as shown in Fig. 1. The tube partitions M are provided with very small pin holes 3| (Fig. 2) so that the air pressure in the three chambers becomes equalized. These small holes, which are made in the partitions before the tube is spliced, offer sufficient resistance to the flow of air so that when one chamber is punctured, the air escapes only slowly from the remaining chambers. Other suitable means may be employed for inflating the tube. The general requirement is that .the air pressure in the three chambers be permitted to become substantially equalized and that the intercommunicating means between the chambers offer sufiicient resistance to the flow of air so that when a blowout occurs the air can escape only slowly from the remaining chamber or chambers.

In operation, it will be evident that when a blowout occurs, and the air is lost from one of the chambers, the remaining chambers support the load safely until the vehicle can be brought to a stop. Even in the event that a puncture occurs in such a position that the air is immediately lost from two of the chambers, the third chamber remains intact and supports the: vehicle for a.

4 suificient length of time to permit the vehicle to be brought to a stop.

It should be noted that the helicoidal partition construction of the three-chambered tube provides more rubber in the partitions than would be the case if the partitions extended simply longitudinally in straight lines along the length of the tube. This enables any section of the tube to stretch and fill out the tire casing with greater ease in case of a blowout, without stretching the rubber nearly to its rupture point, and thus prevents all three chambers from blowing out.

In the helicoidal partition construction, the partitions may be regarded as running essentially diagonally or crosswise in the tire, rather than simply longitudinally or parallel to the axis of the tube. The advantage of this is that the partitions in the tube are better able to resist the centrifugal forces which tend to move a partition against the outside of the tube during revolution of the tire, particularly athigh speeds. This rubbing of the partitions against the tube walls has been a principal cause of the excessively rapid wear frequently encountered in conventional multi-chamber tubes.

Having thus described my invention what I claim and desire to protect by Letters Patent is:

l. A slow-deflation inner tube forpneumatic tires comprising a tube divided into three chambers defined by an outer wall and three equally spaced partitions, said partitions being joined at the center axis of the tube and extending radially in generally curved paths to the outer wall, the length of each of said partitions measured from the axis of the uninfiated tubeto the outer wall being substantially where D is the diameter of the tube cross-section, said partitions being twisted around the axis of the tube to form helicoids, a valve for inflating the chambers, and intercommunicating means between the chambers to permit the air pressure in the chambers to be equalized.

2. A slow-deflation inner tube for pneumatic tires comprisinga tubedivided into three chambers defined by an outer wall and three equally spaced partitions, said partitions being joined at the center axis of the tube and extending radially to the outer wall, the length of each of said partitions measured from the axis of the uninfiated tube to the outer wall being substantially where D is the diameter of the tube cross-section, said partitions being twisted around the axis of the tube to form a helicoid, and a valve for inflating the chambers.

3.A slow-deflation inner tube for pneumatic tires comprising a tube divided into three chambers defined by an outer wall and three equally spaced partitions, said partitions being joined at the center axis of the tube and extending radiallyin generally curved paths to the outer wall, the length of each of said partitions measured from the axis of the uninfiated tube to the outer wall being substantially and a valve for inflating the chambers.

4. In an inner tube construction for pneumatic tires, a tube divided in cross-section into three chambers defined by an outer wall of the tube and three equally spaced partitions joined together at the center axis of the tube and extending radially to the outer wall at points equidistant from each other on the wall, the length of each partition measured from the axis to the outer wall being substantially wall, the sum of the length of any two partitions being equal to the length of the outer uninflated tube wall along the circumference between the two said points formed by said partitions.

THOMAS J. RHODES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,459,529 Griifiths June 19, 1923 1,952,221 Ronneberg Mar. 27, 1934 FOREIGN PATENTS Number Country Date 348,301 France 1901 

